Development of geochemical and mineralogical methods for targeting lower environmental impact secondary copper deposits in the Troodos Massif, Cyprus

The Troodos Massif, Cyprus has been mined since the Bronze age and contains around 90 copper deposits (Robb, 2005). Mining has mainly concentrated on the primary volcanogenic massif sulphide-type deposits containing pyrite and chalcopyrite, with lesser sphalerite. With the recent increase in the price of Cu, the range of exploration targets has been broadened to include lower grade secondary (supergene enrichment) deposits. These form mainly as a result of oxidation of primary pyrite by percolating meteoric fluids which causes a reduction in pH of the fluids and subsequent dissolution of chalcopyrite. Much of the Cu enters the fluid phase and is precipitated at deeper levels as either oxides, above the water table, or as sulphides below it. The mining of secondary deposits offers environmental benefits as secondary copper minerals are more amenable to acid leaching rather than the ore beneficiation and smelting necessary for sulphide ores. The exploration for European Cu also offers financial, other environmental (lower metals miles) and strategic benefits relating to security of supply. The aim of the project is to develop new exploration tools for secondary Cu deposits by testing the hypotheses that: 1) surface gossans can be classified, based on mineralogical and geochemical criteria, into those developed from high- and low-Cu sulphide protoliths; 2) gossans formed from high-Cu protoliths may indicate the existence of secondary copper deposits at depth. The student will carrying out detailed field studies in the Troodos Massif and the collection of gossan samples and ground waters, following methods in Leybourne et al. (2006). Five gossans will be studied: the Phoenix and Three Hills deposits, with known secondary Cu mineralisation; two 'barren' gossan sites, to be identified during fieldwork and from discussions with the Cyprus Geological Survey; and the West Apliki prospect, which is as yet undeveloped (Naden et al., 2006). Samples will be examined using optical and scanning electron microscopy (at the Camborne School of Mines - CSM), and then analysed using QEMSCAN automated mineralogical assessment system (at CSM) and by Position Sensitive Detector - X-ray diffraction (PSD-XRD, at the NHM). Complementary whole-sample major and trace element data will be acquired at CSM using X-ray fluorescence and at the NHM using Inductively Coupled Plasma Optical Emission (ICP-OES) and Mass Spectrometry (ICP-MS). Spatially resolved trace element data will be obtained using Laser Ablation ICP-MS at the NHM, or BGS. A classification scheme for gossans known to be formed from high- and low-Cu protoliths will be devised on the basis of the presence/absence of relict minerals and replacement textures and the mineralogy and elemental composition of weathering phases, including clays. The extent and nature of the weathering in gossans from high-Cu protoliths will be assessed by carrying out mass balance calculations using bulk and mineral geochemical data (including rare earth elements, using the method of Boyle, 2003). The student will receive instruction in field geological mapping and sampling from all three supervisors during two field seasons in Cyprus, of four weeks each, the first to undertake detailed studies at the Phoenix, Three Hills and 'barren' sites and the second to test developed models in a semi-exploration context at the West Apliki prospect. Contacts have been made with EMed (Nikos Adamides) and the Geological Survey Department of the Cyprus government (Dr Eleni Morriseau) ensuring excellent student logistical support. Full training will be given at the NHM in PSD-XRD and geochemical (ICP-OES, ICP-MS and LA-ICP-MS) analysis and at CSM in scanning electron microscopy, X-ray fluorescence and QEMSCAN. For references see Case for Support